please help me in understanding why this computed observable is not able to access observables.

Question

this is the fiddle - http://jsfiddle.net/iRamesh/36N4m/

Not sure why computed observable is not returning any value. I know how to make it working but not sure why t

Answer 1

computed observables are evaluated immediately on creation. In your case, viewModel has not been created yet, so this causes an error.

A couple alternatives:

-Create it outside of your initial object literal:

var viewModel = {
    firstName: ko.observable("r"),
    lastName: ko.observable("j"),
 };
viewModel.fullName = ko.computed(function() {
        return viewModel.firstName();
});

-Create your view model in a function:

var ViewModel = function() {
    this.firstName = ko.observable("r");
    this.lastName = ko.observable("j");
    this.fullName = ko.computed(function() {
            return this.firstName();
    }, this);
};

ko.applyBindings(new ViewModel());